[WIP] Account Removal

[AaronJackson]

@dpslwk nowhere near finished yet, mostly wanting to know whether this approach is ok. basically added an interface called EntityObfuscatableInterface for the function obfuscate. Thought about traits and attribute annotations but not sure if that's a better approach.

in terms of obfuscation so far, if a user performs an account removal:

• remove all roles regardless of whether retain is set.
• clear non-required fields from User (we need to retain name and address for 10 years) - so just the email address at the moment, and unlink it from Account
• clear non-required fields from Profile

for bank transactions, we need to keep those for seven years but I dont see any harm in keeping them longer. I started looking into finding historic transactions which are no longer linked to users - we can keep the amount and linked account, but just erase the description (after 7 years). probably best to have a separate job to go through this view:

CREATE VIEW `vw_historic_unlinked_transactions` AS
SELECT bt.* FROM bank_transactions bt
JOIN accounts a ON bt.account_id = a.id
WHERE a.id NOT IN (
   SELECT DISTINCT(user.account_id) FROM user WHERE user.account_id IS NOT NULL
)
AND bt.transaction_date < DATE_SUB(NOW(),INTERVAL 7 YEAR);

for snackspace transactions, I don't think we need to do anything, but we might to unlink them from a User after they request removal, retaining the actual transactions for statistics.

similar for door logs, unless we decide it would be best to unlink these after 3 years regardless of account deletion.

cheers